(1) Field of the Invention
This invention relates to a semiconductor wafer transport method and semiconductor wafer transport apparatus for transporting a semiconductor wafer. More particularly, this invention is directed to a technique of transporting a heated semiconductor wafer.
(2) Description of the Related Art
In recent years, a semiconductor wafer (hereinafter, appropriately referred to as a “wafer”) tends to be ground to have a thickness of several tens micrometers with a need for a high-density package. Accordingly, a circuit and a bump formed on a surface of the wafer may be damaged from a back grinding process until a dicing process, which leads to reduced manufacturing efficiency.
A dicing process is performed to the wafer having a circuit already formed thereon prior to a back grinding process, whereby only non-defective bear chips are sorted. The bear chips are fixedly arranged in a two-dimensional array on an adhesion sheet joined to a carrier substrate. Here, an electrode surface of the bear chip is directed downward. Then, the bear chips are covered with a resin for renewal of the wafer in a wafer shape (hereinafter, referred to as a “renewed wafer”), and the substrate is separated from the renewed wafer. Thereafter, back grinding is performed to the wafer on an opposite side of the electrode surface. The thinned renewed wafer is adhesively held on a ring frame via a support adhesive tape, and transported to a dicing process where the bear chips are diced from the resin. See Japanese Patent Publication No. 2001-308116.
Reinforcement of the wafer includes another aspect as under. That is, for providing rigidity to the wafer thinned through back grinding, a support member for reinforcement having a larger diameter than the wafer is joined to the wafer via a double-faced adhesive tape. An adhesive is adopted in the double-faced adhesive tape having a heat separation property that reduces or eliminates adhesion due to foaming and expansion from heating. See Japanese Patent Publication No. 2005-116679.
As above, the wafer from which the substrate or the support member is separated is cooled on a holding table where the wafer is to be transported.
In addition to the above aspect of the wafer, the renewed wafer and the substrate are joined together via a double-faced adhesive tape having a heat separation property. In this case, when the renewed wafer is separated from the substrate, resin expands due to heating. In other words, the resin has expansion coefficient higher than the bear chip. Moreover, since the resin has higher expansion coefficient than the bear chip, the resin naturally has higher shrinkage due to cooling than the bear chip.
Consequently, the renewed wafer placed on the holding table under a cooling state is cooled rapidly in a short time, and the renewed wafer may be warped due to difference of shrinkage between the bear chip and the resin associated with temperature changes. Alternatively, cracks may occur in the resin, which leads to reduced rigidity. As a result, there arises a problem that damages of the bear chip and handling errors for the renewed wafer may occur.
When the support member is separated with heating from the wafer subject to a back grinding process and the double-faced adhesive tape remains on the wafer, rapid cooling of the wafer in a short time may lead to largely warping of the wafer due to difference in shrinkage between the double-faced adhesive tape and the wafer associated with temperature changes. Accordingly, such warp may cause the wafer to be damaged.
Moreover, a temperature of the wafer gradually decreases to a given temperature with one holding table, processing is suspended prior to a cooling step, which results such disadvantage as reduced treatment efficiency. Alternatively, two or more holding tables may be provided. However, this may leads to an upsized apparatus configuration.